Concrete and preparation method thereof

Abstract

The invention discloses concrete and a preparation method thereof, and relates to the technical field of building construction. The preparation method of the concrete comprises the following steps: S1, crushing construction waste aggregate, adding a magnetic response material, carrying out plasma surface treatment, and then spraying nano silicon dioxide to obtain recycled aggregate; s2, mixing the recycled aggregate and the fine aggregate, and uniformly stirring to obtain mixed aggregate; s3, mixing sodium silicate and calcium nitrate, performing ultrasonic treatment to obtain a crystal nucleus material, and uniformly mixing the crystal nucleus material with cement, limestone powder, kaolin, a water reducing agent and the mixed aggregate to obtain a cementing material; s4, mixing and stirring the mixed solution of sodium silicate and sodium hydroxide with the cementing material and water, and then adding the fiber material to form a mixture; and S5, treating the mixture in a rotating magnetic field environment, and pouring to form the concrete. The problem that low hydration heat, cracking inhibition and high strength cannot be considered at the same time is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of building construction, and particularly relates to a concrete and a preparation method thereof. Background Art

[0002] As one of the most commonly used building materials in modern civil engineering, the performance of concrete directly affects the safety and durability of engineering structures. In large-scale infrastructure (such as bridges, dams, high-rise building foundations, etc.), the problem of hydration heat of concrete is particularly prominent. The heat released during the hydration process of cement will cause the internal temperature of concrete to rise sharply, forming a significant temperature gradient, and then causing temperature stress. When the stress exceeds the tensile strength of the concrete, it will lead to structural cracking, seriously affecting the engineering quality and service life.

[0003] Currently, the methods for reducing the hydration heat of concrete in the prior art mainly include:

[0004] 1. Using low-heat cement: such as low-heat Portland cement, medium-heat Portland cement, etc. However, the production process of such cement is complex, the cost is high, and the early strength development is slow, which limits its wide application.

[0005] 2. Adding mineral admixtures: such as fly ash, slag powder, silica fume, etc., to reduce the hydration heat by replacing part of the cement. However, the excessive use of admixtures will significantly reduce the early strength of concrete, and the dosage needs to be strictly controlled to avoid negative impacts on durability.

[0006] 3. Optimizing the mix proportion: by reducing the cement dosage, increasing the aggregate content or using a retarder to delay the hydration process. However, this method is likely to cause a decrease in the workability of concrete, an increase in construction difficulty, and limited improvement in the later strength.

[0007] 4. Adding an expansive agent: to reduce the cracking risk by compensating for shrinkage. However, the expansion effect of the expansive agent is difficult to accurately control, and excessive use may cause secondary cracking or volume instability.

[0008] In addition, traditional concrete often has difficulty in simultaneously achieving high strength and high crack resistance while reducing the hydration heat. For example, high-strength concrete usually requires a higher cement dosage, resulting in an increase in hydration heat; while low-hydration heat concrete may not meet the engineering requirements due to insufficient strength. Therefore, developing a concrete preparation technology that can significantly reduce the hydration heat, inhibit cracking, and ensure strength has become an urgent technical problem in this field. Summary of the Invention

[0009] The technical problem to be solved by the present invention is that the existing concrete cannot simultaneously achieve low hydration heat, crack inhibition, and high strength. The purpose is to provide a concrete and a preparation method thereof, which solve the problem of inability to simultaneously achieve low hydration heat, crack inhibition, and high strength.

[0010] The present invention is achieved through the following technical solutions:

[0011] A method for preparing concrete, comprising the following steps:

[0012] S1. After crushing construction waste aggregates, add magnetic response materials, perform three-stage plasma surface treatment, and then spray nano-silica to obtain recycled aggregates;

[0013] S2. Mix the recycled aggregates and fine aggregates and stir evenly to obtain mixed aggregates;

[0014] S3. After mixing sodium silicate and calcium nitrate and performing ultrasonic treatment, obtain crystal nucleus materials. Mix the crystal nucleus materials evenly with cement, limestone powder, kaolin, water reducing agent, and mixed aggregates to obtain cementitious materials;

[0015] S4. Mix a mixed solution of sodium silicate and sodium hydroxide with the cementitious materials and water, stir, and then add fiber materials to form a mixture;

[0016] S5. After treating the mixture in a rotating magnetic field environment, pour it to form concrete.

[0017] As a possible design, the above step S1 specifically includes the following steps:

[0018] S11. Crush the construction waste aggregates to 15 - 25 mm, add magnetic response materials, and then perform three-stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen, perform microwave rough activation to generate a nano-silica layer, then introduce a mixed gas of argon and silane, perform arc activation to deposit silicon on the surface of the nano-silica layer, and finally introduce carbon dioxide for microwave activation and sealing treatment to obtain porous aggregates;

[0019] S12. Spray nano-silica on the surface of the porous aggregates to obtain recycled aggregates.

[0020] As a possible design, the above microwave rough activation is carried out under the conditions of 45 - 55 kW for 10 - 20 min, and the volume ratio of argon to oxygen is 3.8 - 4.3:1;

[0021] The above arc activation is carried out under the conditions of 130 - 150 A for 3 - 8 min, and the volume ratio of argon to silane is 93 - 95:5;

[0022] The above microwave activation is carried out under the conditions of 3 - 5 kW for 1 - 3 min;

[0023] The thickness of the nano-silica coating is 130 - 190 nm.

[0024] As a possible design, the above S3 includes the following steps:

[0025] S31. Mix sodium silicate and calcium nitrate in a ratio of calcium to silicon molar ratio of 1 - 1.3:1, treat under the condition of 35 - 45 kHz for 1 - 2 h, and dry to obtain the crystal nucleus material;

[0026] S32. Mix the crystal nucleus material, cement, limestone powder, kaolin, water reducing agent and mixed aggregate evenly to obtain the cementitious material.

[0027] As a possible design, the above S4 includes the following steps:

[0028] S41. Mix sodium silicate and sodium hydroxide in a weight ratio of (2.5 - 3.5):1, adjust the pH value to 12.5 - 13.5 to obtain a mixed solution;

[0029] S42. Mix the mixed solution, cementitious material and water evenly, and then add the fiber material in 2 - 4 times and stir evenly to form a mixture.

[0030] As a possible design, the treatment under the rotating magnetic field environment includes treating the mixture under a rotating magnetic field of 0.4 - 0.6 T and 6 - 8 Hz for 3 - 4 min.

[0031] A kind of concrete, comprising the following raw materials in parts by weight:

[0032] Construction waste aggregate 300 - 400 parts, fine aggregate 100 - 200 parts, magnetic response material 2 - 4 parts, crystal nucleus material 3 - 6 parts, cement 180 - 230 parts, limestone powder 30 - 60 parts, kaolin 130 - 150 parts, fiber material 1 - 3 parts, water reducing agent 5 - 15 parts, mixed solution 50 - 80 parts and water 50 - 150 parts.

[0033] As a possible design, the above magnetic response material includes magnetite nanoparticles.

[0034] As a possible design, the particle size of the above magnetite is 20 - 50 nm.

[0035] As a possible design, the above fiber material includes basalt fiber;

[0036] The mixed solution includes sodium silicate and sodium hydroxide in a weight ratio of (2.5 - 3.5):1.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] In the present invention, construction waste aggregates are subjected to three - stage plasma surface reconstruction to obtain a helical porous structure, improving the surface characteristics and stability of the materials, enhancing the interfacial bonding strength between the aggregates and the paste. Then, a silica coating is applied on the surface to reduce the thickness of the interfacial transition zone and improve the tensile strength, thereby increasing the strength of the subsequent concrete. Additionally, adding kaolin and limestone powder reduces the amount of cement used and the heat of hydration. Meanwhile, the nucleating material can serve as a nucleation site, converting disordered C - S - H gel into crystalline tobermorite, further reducing the heat of hydration. With the aid of fiber and rotating magnetic field treatment, the gelling material forms a layered structure along the magnetic field direction, thus increasing the elastic modulus and inhibiting cracking. Detailed implementation manners

[0039] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. The illustrative implementation manners and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0040] A method for preparing concrete includes the following steps:

[0041] S1. After crushing the construction waste aggregates, add magnetic - responsive materials, perform three - stage plasma surface treatment, and then spray nano - silica to obtain recycled aggregates.

[0042] By utilizing the interaction between the active particles in the plasma and the material surface, the surface physical and chemical properties of the aggregates are changed. Specifically, the high - energy particles in the plasma bombard the material surface, breaking the macromolecular chains on the surface layer. The formed small molecules volatilize, resulting in a reduction of the surface substances of the material, making the surface rough, increasing the specific surface area of the material. At the same time, the free radicals on the surface combine with active particles such as oxygen in the plasma discharge region, thereby introducing polar groups with strong reactivity. Multiple effects enable the aggregates to obtain a helical porous structure. Subsequently, by generating a nano - silica layer and a calcium carbonate dense layer in sequence to fill the micro - cracks, the ion permeability can be reduced and the concrete strength can be enhanced.

[0043] In some embodiments of the present invention, the above - mentioned step S1 specifically includes the following steps:

[0044] S11. Crush the construction waste aggregates to 15 - 25 mm, add magnetic - responsive materials, and then perform three - stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen for microwave rough activation to generate a nano - silica layer, then introduce a mixed gas of argon and silane for arc activation to deposit silicon on the surface of the nano - silica layer, and finally introduce carbon dioxide for microwave activation for sealing treatment to obtain porous aggregates.

[0045] Crushing can increase the specific surface area. Then, high-energy particles in the plasma bombard the surface of the aggregate to generate an amorphous SiO2 active layer, which can significantly improve the chemical bonding ability with the paste. Then, through arc activation, SiH4 is cracked into Si nanoparticles, which are embedded in the pores of the aggregate by precise point adsorption to improve the interlocking effect. Then, through carbon dioxide hole sealing treatment, specifically, microwave activation decomposes CO2 into active oxygen, which reacts with surface Ca to form nano-CaCO3, which can form a dense calcium carbonate layer to fill microcracks, reduce the ion permeability, further improve the surface characteristics and stability of the material, and effectively improve the interfacial bonding strength between the aggregate and the paste.

[0046] The above microwave rough activation is carried out under the conditions of 45 - 55 kW for 10 - 20 min;

[0047] The above arc activation is carried out under the conditions of 130 - 150 A for 3 - 8 min;

[0048] The above microwave activation is carried out under the conditions of 3 - 5 kW for 1 - 3 min.

[0049] In some embodiments of the present invention, the volume ratio of the above argon to oxygen is 3.8 - 4.3:1; the volume ratio of argon to silane is 93 - 95:5.

[0050] The above magnetic response material includes Fe3O4 nanoparticles. Preferably, the particle size of Fe3O4 is 20 - 50 nm. The Fe3O4 nanoparticles are anchored on the surface of the aggregate by the bombardment of high-energy particles in the plasma to form a magnetized interface transition layer, endowing the aggregate with magnetic response ability without damaging the mechanical properties of the aggregate.

[0051] S12. Spray nano-silica on the surface of the porous aggregate to obtain a recycled aggregate.

[0052] By spraying nano-silica, the interfacial bonding strength can be improved, the surface roughness can be increased, and a better mechanical interlocking effect can be provided for the cement matrix; at the same time, the nano-SiO2 particles are small in size and can fill the tiny pores and cracks on the surface of the aggregate, making the surface of the aggregate more dense and flat. This dense surface reduces the pores and defects between the aggregate and the cement matrix, enhances the continuity and stability of the interface, and thus improves the interfacial bonding strength; nano-SiO2 has high activity and can react with the hydration products in the cement matrix to form more calcium silicate hydrate (C-S-H) gels, improving the subsequent chemical bonding effect.

[0053] In some embodiments of the present invention, the thickness of the above nano-silica coating is 130 - 190 nm.

[0054] S2. Mix the recycled aggregate and fine aggregate and stir evenly to obtain a mixed aggregate.

[0055] S3. After mixing sodium silicate and calcium nitrate and subjecting them to ultrasonic treatment, a crystal nucleus material is obtained. The crystal nucleus material is mixed evenly with cement, limestone powder, kaolin, water reducer and the mixed aggregate to obtain a cementitious material.

[0056] The mixture of various materials has excellent cementitious activity, which is convenient for subsequent use.

[0057] In some embodiments of the present invention, the above S3 includes the following steps:

[0058] S31. Mix sodium silicate and calcium nitrate in a calcium-silicon molar ratio of 1 - 1.3:1, treat them under the condition of 35 - 45 kHz for 1 - 2 h, and dry to obtain the crystal nucleus material.

[0059] Sodium silicate and calcium nitrate undergo hydrolysis and polycondensation reactions to obtain a gel precursor with a specific chemical composition and structure. With the aid of ultrasonic oscillation, the mixed solution can be made more uniform, reducing the agglomeration phenomenon, which is beneficial to the formation of crystal nucleus materials with smaller size and uniform distribution.

[0060] The above drying is spray drying.

[0061] S32. Mix the crystal nucleus material evenly with cement, limestone powder, kaolin, water reducer and the mixed aggregate to obtain a cementitious material.

[0062] S4. Mix the mixed solution of sodium silicate and sodium hydroxide with the cementitious material and water, and then add fiber materials to form a mixture.

[0063] In some embodiments of the present invention, the above S4 includes the following steps:

[0064] S41. Mix sodium silicate and sodium hydroxide in a weight ratio of (2.5 - 3.5):1, adjust the pH value to 12.5 - 13.5 to obtain a mixed solution.

[0065] When sodium silicate and calcium nitrate are mixed, an ion exchange reaction occurs, generating calcium silicate precipitate insoluble in water and sodium nitrate.

[0066] S42. Mix the mixed solution evenly with the cementitious material and water, and then add fiber materials in 2 - 4 times and stir evenly to form a mixture.

[0067] In the cementitious material, the crystal nucleus material serves as a nucleation site, causing the hydration products of cement to transform from amorphous C-S-H gel to crystalline tobermorite, reducing the porosity and lowering the hydration heat release rate. At the same time, the mixed solution can provide a highly alkaline environment, stimulating the pozzolanic activity of materials such as kaolin and enabling them to participate in the secondary hydration reaction to generate more C-S-H gel, reducing the porosity and further enhancing the strength and durability of the concrete. Limestone and kaolin can play a filling role, improving the pore structure of the concrete and enhancing its compactness. The fiber material is added in batches, which can avoid agglomeration and enhance the crack resistance of the concrete.

[0068] In some embodiments of the present invention, the above-mentioned fiber material includes basalt fiber.

[0069] S5. After treating the mixture in a rotating magnetic field environment, pour it to form concrete.

[0070] In some embodiments of the present invention, the treatment in the rotating magnetic field environment includes treating the mixture in a rotating magnetic field of 0.4 - 0.6 T and 6 - 8 Hz for 3 - 4 min.

[0071] Through the treatment with a rotating magnetic field, it is possible to affect the movement of charged particles inside the concrete, promote the cement hydration reaction, make the hydration products more evenly distributed, form a dense structure, improve the strength and durability of the concrete; it can also improve the internal stress distribution of the concrete and reduce the microcracks caused by stress concentration.

[0072] A kind of concrete, comprising the following raw materials in parts by weight:

[0073] Construction waste aggregate 300 - 400 parts, fine aggregate 100 - 200 parts, magnetic response material 2 - 4 parts, crystal nucleus material 3 - 6 parts, cement 180 - 230 parts, limestone powder 30 - 60 parts, kaolin 130 - 150 parts, fiber material 1 - 3 parts, water reducing agent 5 - 15 parts, mixed solution 50 - 80 parts, and water 50 - 150 parts.

[0074] Preferably, the water reducing agent is a polycarboxylate water reducing agent.

[0075] In some embodiments of the present invention, the above-mentioned magnetic response material includes magnetite nanoparticles.

[0076] In some embodiments of the present invention, the particle size of the above-mentioned magnetite is 20 - 50 nm.

[0077] In some embodiments of the present invention, the above-mentioned fiber material includes basalt fiber;

[0078] The mixed solution includes sodium silicate and sodium hydroxide in a weight ratio of (2.5 - 3.5):1.

[0079] Example 1

[0080] A preparation method of concrete, comprising the following steps:

[0081] Raw materials:

[0082] 300 g of construction waste aggregate, 100 g of fine aggregate, 3 g of magnetic response material, 4 g of crystal nucleus material, 180 g of cement, 30 g of limestone powder, 130 g of kaolin, 3 g of fiber material, 15 g of water reducing agent, 50 g of mixed solution and 80 g of water.

[0083] S1. Crush the construction waste aggregate to 15 - 25 mm, add the magnetic response material, and then perform three - stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen with a ratio of 3.8:1, first perform microwave rough activation for 10 min under the condition of 45 kW to generate a nano - silica layer, then introduce a mixed gas of argon and silane with a ratio of 93:5, perform arc activation for 3 min under the condition of 130 A to deposit silicon on the surface of the nano - silica layer, and finally introduce carbon dioxide and perform microwave activation for 1 min under the condition of 3 kW for pore - sealing treatment to obtain porous aggregate.

[0084] S2. Mix the recycled aggregate and the fine aggregate, and stir evenly to obtain a mixed aggregate.

[0085] S3. Mix sodium silicate and calcium nitrate according to a calcium - silicon molar ratio of 1:1, treat under the condition of 35 kHz for 1 h, and perform spray drying to obtain the crystal nucleus material; mix the crystal nucleus material with cement, limestone powder, kaolin, water reducing agent and the mixed aggregate evenly to obtain the cementitious material.

[0086] S4. Mix sodium silicate and sodium hydroxide according to a weight ratio of 2.5:1, adjust the pH value to 12.5 to obtain a mixed solution; mix the mixed solution with the cementitious material and water evenly, and then add the fiber material in 2 portions and stir evenly to form a mixture.

[0087] S5. After treating the mixture under a rotating magnetic field of 0.4 T and 6 Hz for 3 min, pour it to form concrete.

[0088] Example 2

[0089] A preparation method of concrete, comprising the following steps:

[0090] Raw materials:

[0091] 350 g of construction waste aggregate, 150 g of fine aggregate, 3 g of magnetic response material, 3 g of crystal nucleus material, 210 g of cement, 50 g of limestone powder, 140 g of kaolin, 2 g of fiber material, 12 g of water reducing agent, 60 g of mixed solution and 100 g of water.

[0092] S1. Crush the construction waste aggregate to 15 - 25 mm, add the magnetic response material, and then perform three - stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen with a ratio of 4:1, and first perform microwave rough activation for 15 min under the condition of 50 kW to generate a nano - silica layer. Then introduce a mixed gas of argon and silane with a ratio of 94:5, and perform arc activation for 5 min under the condition of 140 A to deposit silicon on the surface of the nano - silica layer. Finally, introduce carbon dioxide and perform microwave activation for 2 min under the condition of 4 kW for sealing treatment to obtain a porous aggregate.

[0093] S2. Mix the recycled aggregate and the fine aggregate evenly to obtain a mixed aggregate.

[0094] S3. Mix sodium silicate and calcium nitrate according to a calcium - silicon molar ratio of 1.2:1, treat for 1.5 h under the condition of 45 kHz, and perform spray drying to obtain a crystal nucleus material; mix the crystal nucleus material, cement, limestone powder, kaolin, water - reducing agent and the mixed aggregate evenly to obtain a cementitious material.

[0095] S4. Mix sodium silicate and sodium hydroxide according to a weight ratio of 3:1, adjust the pH value to 13 to obtain a mixed solution; mix the mixed solution, the cementitious material and water evenly, and then add the fiber material in 3 times and stir evenly to form a mixture.

[0096] S5. After treating the mixture under a rotating magnetic field of 0.5 T and 7 Hz for 3.5 min, pour it to form concrete.

[0097] Example 3

[0098] A method for preparing concrete, comprising the following steps:

[0099] Raw materials:

[0100] 400 g of construction waste aggregate, 200 g of fine aggregate, 4 g of magnetic response material, 6 g of crystal nucleus material, 230 g of cement, 60 g of limestone powder, 150 g of kaolin, 3 g of fiber material, 15 g of water - reducing agent, 80 g of mixed solution and 150 g of water.

[0101] S1. Crush the construction waste aggregate to 25 mm, add the magnetic response material, and then perform three - stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen with a ratio of 4.3:1, and first perform microwave rough activation for 20 min under the condition of 55 kW to generate a nano - silica layer. Then introduce a mixed gas of argon and silane with a ratio of 95:5, and perform arc activation for 8 min under the condition of 150 A to deposit silicon on the surface of the nano - silica layer. Finally, introduce carbon dioxide and perform microwave activation for 3 min under the condition of 5 kW for sealing treatment to obtain a porous aggregate.

[0102] S2. Mix the recycled aggregate and fine aggregate, and stir evenly to obtain a mixed aggregate.

[0103] S3. Mix sodium silicate and calcium nitrate in a calcium-silicon molar ratio of 1.3:1, treat under the condition of 45 kHz for 2 h, and spray dry to obtain a nucleating material; mix the nucleating material with cement, limestone powder, kaolin, water reducer and mixed aggregate evenly to obtain a cementitious material.

[0104] S4. Mix sodium silicate and sodium hydroxide in a weight ratio of 3.5:1, adjust the pH value to 113.5 to obtain a mixed solution; mix the mixed solution with the cementitious material and water evenly, and then add the fiber material in 4 times and stir evenly to form a mixture.

[0105] S5. After treating the mixture under a rotating magnetic field of 0.6 T and 8 Hz for 4 min, pour it to form concrete.

[0106] Comparative Example 1

[0107] This comparative example is basically the same as Example 2, the difference is that: the construction waste aggregate is not subjected to three-stage plasma surface treatment.

[0108] A method for preparing concrete, comprising the following steps:

[0109] Raw materials:

[0110] 350 g of construction waste aggregate, 150 g of fine aggregate, 3 g of magnetic response material, 3 g of nucleating material, 210 g of cement, 50 g of limestone powder, 140 g of kaolin, 2 g of fiber material, 12 g of water reducer, 60 g of mixed solution and 100 g of water.

[0111] S1. Crush the construction waste aggregate to 15 - 25 mm, add the magnetic response material and mix evenly, and then spray nano-silica on the surface to obtain recycled aggregate.

[0112] S2. Mix the recycled aggregate and fine aggregate, and stir evenly to obtain a mixed aggregate.

[0113] S3. Mix sodium silicate and calcium nitrate in a calcium-silicon molar ratio of 1.2:1, treat under the condition of 45 kHz for 1.5 h, and spray dry to obtain a nucleating material; mix the nucleating material with cement, limestone powder, kaolin, water reducer and mixed aggregate evenly to obtain a cementitious material.

[0114] S4. Mix sodium silicate and sodium hydroxide in a weight ratio of 3:1, adjust the pH value to 13 to obtain a mixed solution; mix the mixed solution with the cementitious material and water evenly, and then add the fiber material in 3 times and stir evenly to form a mixture.

[0115] S5. After treating the mixture under a rotating magnetic field of 0.5 T and 7 Hz for 3.5 min, pour it to form concrete.

[0116] Comparative Example 2

[0117] This comparative example is basically the same as Example 2, except that: silicon is not deposited on the surface of the nano-silica layer.

[0118] Comparative Example 3

[0119] This comparative example is basically the same as Example 2, except that: the magnetic response material is not added and the rotating magnetic field treatment is not carried out.

[0120] A method for preparing concrete, comprising the following steps:

[0121] Raw materials:

[0122] 350 g of construction waste aggregate, 150 g of fine aggregate, 3 g of magnetic response material, 3 g of crystal nucleus material, 210 g of cement, 50 g of limestone powder, 140 g of kaolin, 2 g of fiber material, 12 g of water reducing agent, 60 g of mixed solution and 100 g of water.

[0123] S1. Crush the construction waste aggregate to 15 - 25 mm, and then carry out three-stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen with a ratio of 4:1, first carry out microwave rough activation treatment at 50 kW for 15 min to generate a nano-silica layer, then introduce a mixed gas of argon and silane with a ratio of 94:5, carry out arc activation at 140 A for 5 min for arc activation, deposit silicon on the surface of the nano-silica layer, and finally introduce carbon dioxide to carry out microwave activation at 4 kW for 2 min for microwave activation and sealing treatment to obtain porous aggregate.

[0124] S2. Mix the recycled aggregate and the fine aggregate and stir evenly to obtain a mixed aggregate.

[0125] S3. Mix sodium silicate and calcium nitrate according to a calcium-silicon molar ratio of 1.2:1, treat it at 45 kHz for 1.5 h, and spray dry to obtain a crystal nucleus material; mix the crystal nucleus material with cement, limestone powder, kaolin, water reducing agent and mixed aggregate evenly to obtain a cementitious material.

[0126] S4. Mix sodium silicate and sodium hydroxide according to a weight ratio of 3:1, adjust the pH value to 13 to obtain a mixed solution; mix the mixed solution with the cementitious material and water and stir evenly, and then add the fiber material in 3 times and stir evenly to form a mixture, and pour it to form concrete.

[0127] Comparative Example 4

[0128] This comparative example is basically the same as Example 2, except that: the mixed solution is not added.

[0129] A preparation method of concrete, comprising the following steps:

[0130] Raw materials:

[0131] 350 g of construction waste aggregate, 150 g of fine aggregate, 3 g of magnetic response material, 3 g of crystal nucleus material, 210 g of cement, 50 g of limestone powder, 140 g of kaolin, 2 g of fiber material, 12 g of water reducing agent and 100 g of water.

[0132] S1. Crush the construction waste aggregate to 15 - 25 mm, add the magnetic response material, and then perform three - stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen with a ratio of 4:1, first perform microwave rough activation treatment for 15 min under the condition of 50 kW to generate a nano - silica layer, then introduce a mixed gas of argon and silane with a ratio of 94:5, perform arc activation for 5 min under the condition of 140 A to deposit silicon on the surface of the nano - silica layer, and finally introduce carbon dioxide and perform microwave activation for 2 min under the condition of 4 kW for pore - sealing treatment to obtain porous aggregate. S2. Mix the recycled aggregate and the fine aggregate and stir evenly to obtain a mixed aggregate.

[0133] S3. Mix sodium silicate and calcium nitrate according to a calcium - silicon molar ratio of 1.2:1, treat for 1.5 h under the condition of 45 kHz, and perform spray drying to obtain the crystal nucleus material; mix the crystal nucleus material with cement, limestone powder, kaolin, water reducing agent and the mixed aggregate evenly to obtain a cementitious material.

[0134] S4. Add the fiber material and water to the cementitious material in 3 portions and stir evenly to form a mixture.

[0135] S5. Treat the mixture under a rotating magnetic field of 0.5 T and 7 Hz for 3.5 min, and then pour it to form concrete.

[0136] Experimental examples

[0137] For the concrete of Examples 1 - 3 and Comparative Examples 1 - 4 respectively, test the cube compressive strength, splitting tensile strength and flexural strength of high - strength recycled concrete according to GB / T 50081 - 2019. Each group of test specimens has 3 samples, and the result takes the average value of the three.

[0138] The size of the test piece is: 150 mm×150 mm×150 mm.

[0139] Cube compressive strength test: Place the test specimens cured for 28 d on the bearing plate surface of a servo - hydraulic testing machine, and the test loading rate is taken as 0.5 MPa / s.

[0140] Splitting tensile strength test: Draw parallel lines in the middle of the top and bottom surfaces of the test specimens cured for 28 days to determine the position of the splitting surface. Place them in the splitting mold and at the center position of the bearing plate surface of the servo hydraulic testing machine. Apply load evenly during the test, with a loading rate of 0.05 MPa / s, and record the load-displacement curve throughout the test process.

[0141] Flexural strength test: Draw the load application line positions on the sides of the test specimens cured for 28 days. Apply load evenly during the test, with a loading rate of 0.05 MPa / s, and record the load-displacement curve throughout the test process.

[0142] The experimental results are shown in Table 1.

[0143] Table 1

[0144]

[0145]

[0146] It can be observed that the comprehensive performance of Example 2 of the present invention is the best.

[0147] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing concrete, characterized in that, It includes the following steps: S1. After crushing the construction waste aggregate, add a magnetic response material, conduct three-stage plasma surface treatment, and then spray nano-silica to obtain recycled aggregate; S2. Mix the recycled aggregate and fine aggregate and stir evenly to obtain a mixed aggregate; S3. After mixing sodium silicate and calcium nitrate and subjecting them to ultrasonic treatment, obtain a crystal nucleus material. Mix the crystal nucleus material with cement, limestone powder, kaolin, water reducer, and mixed aggregate evenly to obtain a cementitious material; S4. Mix the mixed solution of sodium silicate and sodium hydroxide with the cementitious material and water, stir, and then add fiber material to form a mixture; S5. After treating the mixture in a rotating magnetic field environment, pour it to form concrete.

2. The preparation method of a kind of concrete according to claim 1, characterized in that, Step S1 specifically includes the following steps: S11. Crush the construction waste aggregate to 15 - 25 mm, add a magnetic response material, and then conduct three-stage plasma surface treatment. Specifically, first introduce a mixed gas of argon and oxygen, conduct microwave rough activation to generate a nano-silica layer, then introduce a mixed gas of argon and silane, conduct arc activation to deposit silicon on the surface of the nano-silica layer, and finally introduce carbon dioxide for microwave activation and sealing treatment to obtain a porous aggregate; S12. Spray nano-silica on the surface of the porous aggregate to obtain recycled aggregate.

3. A method for preparing concrete according to claim 2, wherein, The microwave rough activation is carried out under the condition of 45 - 55 kW for 10 - 20 min, and the volume ratio of argon to oxygen is 3.8 - 4.3:1; The arc activation is carried out under the condition of 130 - 150 A for 3 - 8 min, and the volume ratio of argon to silane is 93 - 95:5; The microwave activation is carried out under the condition of 3 - 5 kW for 1 - 3 min; The thickness of the nano-silica coating is 130 - 190 nm.

4. A method for preparing concrete according to claim 1, characterized in that, S3 includes the following steps: S31. Mix sodium silicate and calcium nitrate according to the calcium-silicon molar ratio of 1 - 1.3:1, treat under the condition of 35 - 45 kHz for 1 - 2 h, and dry to obtain a crystal nucleus material; S32. Mix the crystal nucleus material with cement, limestone powder, kaolin, water reducer, and mixed aggregate evenly to obtain a cementitious material.

5. A method for preparing concrete according to claim 1, characterized in that, S4 includes the following steps: S41. Mix sodium silicate and sodium hydroxide according to the weight ratio of (2.5 - 3.5):1, adjust the pH value to 12.5 - 13.5 to obtain a mixed solution; S42. Mix the mixed solution with the cementitious material and water evenly, and then add the fiber material in 2 - 4 times and stir evenly to form a mixture.

6. A method for preparing concrete according to claim 1, characterized in that, The treatment under the rotating magnetic field environment includes treating the mixture under a rotating magnetic field of 0.4 - 0.6 T and 6 - 8 Hz for 3 - 4 min.

7. A kind of concrete, characterized in that, It includes the following raw materials in parts by weight: 300 - 400 parts of construction waste aggregate, 100 - 200 parts of fine aggregate, 2 - 4 parts of magnetic response material, 3 - 6 parts of crystal nucleus material, 180 - 230 parts of cement, 30 - 60 parts of limestone powder, 130 - 150 parts of kaolin, 1 - 3 parts of fiber material, 5 - 15 parts of water reducer, 50 - 80 parts of mixed solution, and 50 - 150 parts of water.

8. A concrete according to claim 7, characterized in that, The magnetic response material includes magnetite nanoparticles.

9. A concrete according to claim 8, characterized in that, The particle size of the magnetite is 20 - 50 nm.

10. A concrete according to claim 7, characterized in that, The fiber material includes basalt fiber; The mixed solution includes sodium silicate and sodium hydroxide in a weight ratio of (2.5 to 3.5):1.

Images